深层平板试验和单桩竖向抗压静载试验的对比分析
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摘要
根据Mindlin理论弹性位移解,结合有限元算例,分析了在同等荷载工作条件下深层平板和单桩竖向抗压静载试验的竖向位移差异。深层平板与单桩竖向抗压静载试验产生的竖向位移的比值,随着桩径的增大而减小,在常规桩径0.8~2.0 m范围内,两者的比值为3.2~4.6倍。工程实例发现,两者的比值可达4.5~7.2倍。因此,深层平板载荷试验不能充分挖掘单桩竖向受力潜能,其试验结果不能真实反应单桩竖向受力性能,不应采用深层平板载荷试验确定桩端承载力,而应采用单桩竖向抗压静载试验确定承载力。
Based on the Mindlin elastic displacement solution and combined with finite element numerical example,the analysis is made on the vertical deformation difference of deep plate test and single pile vertical compressive static load test under the same load condition.The ratio of vertical displacement resulted from these 2 tests decreases with the increase of pile diameter,and the ratio is 3.2~4.6 while the conventional pile diameters are within the range of 0.8~2.0 m.The engineering example shows that the ratio of the both can be 4.5~7.2 times.Therefore,single pile vertical load-bearing potential can not be fully exploited in the deep plate loading test and the test results can not truly reflect the single pile vertical load-bearing performance.The bearing capacity of pile tip should be determined by single pile vertical compressive static load test rather than deep plate loading test.
Based on the Mindlin elastic displacement solution and combined with finite element numerical example,the analysis is made on the vertical deformation difference of deep plate test and single pile vertical compressive static load test under the same load condition.The ratio of vertical displacement resulted from these 2 tests decreases with the increase of pile diameter,and the ratio is 3.2~4.6 while the conventional pile diameters are within the range of 0.8~2.0 m.The engineering example shows that the ratio of the both can be 4.5~7.2 times.Therefore,single pile vertical load-bearing potential can not be fully exploited in the deep plate loading test and the test results can not truly reflect the single pile vertical load-bearing performance.The bearing capacity of pile tip should be determined by single pile vertical compressive static load test rather than deep plate loading test.
引文
[1]JGJ 94—2008,建筑桩基技术规范[S].
[2]JGJ/T 225—2010,大直径扩底灌注桩技术规程[S].
[3]Harry G.Poulos,Edward H.Davis.孙幼兰译.岩土力学弹性解[M].江苏南京:中国矿业大学出版社,1990.
[4]GB 50021—2001,岩土工程勘察规范(2009年版)[S].
[5]顾宝和,周红,朱小林,等.深层平板静力载荷试验测定土的变形模量[J].工程勘察,2000,(4):1-2,6.
[6]岳建勇,高大钊,等.再论“深层平板静力载荷试验测定土的变形模量”[J].工程勘察,2002,(1):8-10,28.
[7]编委会.工程地质手册(第四版)[M].北京:中国建筑工业出版社,2006.
[8]高广运,蒋建平,顾宝和,等.两种静载试验确定大直径扩底桩竖向承载力[J].地下空间,2003,23(3):272-276.
[2]JGJ/T 225—2010,大直径扩底灌注桩技术规程[S].
[3]Harry G.Poulos,Edward H.Davis.孙幼兰译.岩土力学弹性解[M].江苏南京:中国矿业大学出版社,1990.
[4]GB 50021—2001,岩土工程勘察规范(2009年版)[S].
[5]顾宝和,周红,朱小林,等.深层平板静力载荷试验测定土的变形模量[J].工程勘察,2000,(4):1-2,6.
[6]岳建勇,高大钊,等.再论“深层平板静力载荷试验测定土的变形模量”[J].工程勘察,2002,(1):8-10,28.
[7]编委会.工程地质手册(第四版)[M].北京:中国建筑工业出版社,2006.
[8]高广运,蒋建平,顾宝和,等.两种静载试验确定大直径扩底桩竖向承载力[J].地下空间,2003,23(3):272-276.